Message-ID: <2cfba291-656f-9a43-fdd5-7601a6fe6ef5@linaro.org>
Date:   Fri, 3 Mar 2023 11:40:53 +0000
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Subject: Re: [RFC PATCH] interconnect: qcom: icc-rpm: Don't call
 __qcom_icc_set twice on the same node
Content-Language: en-US
To:     Konrad Dybcio <konrad.dybcio@linaro.org>,
        linux-arm-msm@vger.kernel.org, andersson@kernel.org,
        agross@kernel.org
Cc:     marijn.suijten@somainline.org, Georgi Djakov <djakov@kernel.org>,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20230303023500.2173137-1-konrad.dybcio@linaro.org>
 <59b28fb4-1367-9872-ed63-90847e380bb6@linaro.org>
 <29513b9e-8561-7f7e-370e-7515116c7ee6@linaro.org>
 <3116a08a-30a8-c9b9-f079-26739c9e6d49@linaro.org>
 <08020872-6316-8f81-ac6a-c6eef408818f@linaro.org>
 <db4f4e53-e8b9-0807-7490-2c6b76194ad5@linaro.org>
From:   Bryan O'Donoghue <bryan.odonoghue@linaro.org>
In-Reply-To: <db4f4e53-e8b9-0807-7490-2c6b76194ad5@linaro.org>
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On 03/03/2023 11:39, Konrad Dybcio wrote:
> 
> 
> On 3.03.2023 12:36, Bryan O'Donoghue wrote:
>> On 03/03/2023 11:35, Bryan O'Donoghue wrote:
>>> On 03/03/2023 11:33, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 3.03.2023 12:32, Bryan O'Donoghue wrote:
>>>>> On 03/03/2023 02:35, Konrad Dybcio wrote:
>>>>>> Currently, when sync_state calls set(n, n) all the paths for setting
>>>>>> parameters on an icc node are called twice. Avoid that.
>>>>>>
>>>>>> Fixes: 751f4d14cdb4 ("interconnect: icc-rpm: Set destination bandwidth as well as source bandwidth")
>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>>>> ---
>>>>>> RFC comes from the fact that I *believe* this should be correct, but I'm
>>>>>> not entirely sure about it..
>>>>>>
>>>>>>
>>>>>>     drivers/interconnect/qcom/icc-rpm.c | 2 +-
>>>>>>     1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/interconnect/qcom/icc-rpm.c b/drivers/interconnect/qcom/icc-rpm.c
>>>>>> index a6e0de03f46b..d35db1af9b08 100644
>>>>>> --- a/drivers/interconnect/qcom/icc-rpm.c
>>>>>> +++ b/drivers/interconnect/qcom/icc-rpm.c
>>>>>> @@ -387,7 +387,7 @@ static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>>>>>>         ret = __qcom_icc_set(src, src_qn, sum_bw);
>>>>>>         if (ret)
>>>>>>             return ret;
>>>>>> -    if (dst_qn) {
>>>>>> +    if (dst_qn && src_qn != dst_qn) {
>>>>>>             ret = __qcom_icc_set(dst, dst_qn, sum_bw);
>>>>>>             if (ret)
>>>>>>                 return ret;
>>>>>
>>>>> Is it possible for src_qn == dst_qn ?
>>>> As the commit message says, sync_state calls set(n, n) in
>>>> drivers/interconnect/core.c : icc_sync_state(struct device *dev)
>>>
>>> So you've _seen_ that happen ?
>>>
>>
>> Assuming you have, then why isn't the fix in sync_state i.e. that's an error for everybody right ?
> I believe that there's simply no other way of updating every single node
> on its own with the icc api, without taking any links into play. But I
> see exynos and i.mx also effectively calling it twice on each node.
> 
> Konrad

I mean. I'm fine for you to retain my RB on this qcom specific patch 
since this seems like a real bug to me but... it seems like a generic 
bug across arches that should probably be resolved @ the higher level.

?

---
bod